This invention relates generally to optical data transmission devices and, more particularly, this invention relates to thermal management and yield of secondary assembly for optical mirror modules.
Optical networks generally are considered the data transmission medium of choice in the networking field. Among other advantages, optical networks generally have a higher bandwidth and lower power/line loss than those that are electrically based. To that end, optical fibers carrying data typically connect with a switching device that translates optical signals into electrical signals. After they are translated, the electrical signals then are routed by the switch, and then translated back into optical signals for delivery to the next optical fiber.
It is more efficient and less costly, however, to route high bandwidth signals solely in the optical domain. In other words, eliminating the process of translating signals between the optical and electrical domains improves switch efficiency. This type of switching device (referred to as an xe2x80x9coptical switchxe2x80x9d) typically has one or more movable internal mirrors that reflect light beams between optical fibers. One such exemplary type of optical switching device is known as an xe2x80x9coptical cross connect switch.xe2x80x9d This type of switch (e.g., a MEMS mirror based optical cross connect switch) typically has an array of mirrors that each have a reflective metallization (e.g., gold) on its surface. This reflective metallization (or the curvature of the mirror itself) undesirably can be altered, however, if subjected to relatively high temperatures for a sustained period of time. Such temperatures typically are greater than 200 degrees centigrade.
In addition, high packaging process temperatures can create substantial mechanical stresses during or after assembly, consequently negatively impacting product performance. Accordingly, to maintain the integrity of such an optical cross-connect switch, it is important to ensure that it is not exposed to such relatively high temperatures.
In accordance with one aspect of the invention, an optical mirror module has an interface port that is spaced from a corresponding die. More specifically, the optical mirror module includes a substrate and a die having at least one mirror and circuitry to control the at least one mirror. The die has a length dimension. The optical mirror module defines a plane that is substantially parallel to the die along its length dimension. The optical mirror module further includes the noted interface port, which is adapted to electrically couple the circuitry with a device external to the optical mirror module. As suggested above, the interface port is located on the substrate and spaced from the die in a direction that is substantially parallel to the plane.
In illustrative embodiments, the substrate has a first surface and a second surface, where the interface port is located on at least one of the first surface and the second surface. The first surface may have a first surface edge portion, where the interface port is located in the first surface edge portion. In addition, the first surface may be either substantially orthogonal to the plane, or substantially parallel to the plane.
Among other materials, the substrate may include aluminum nitride. The optical mirror module also may include a hermetic layer that hermetically seals at least a portion of the die. A flexible circuit may be coupled with at least one of the interface ports.
In accordance with another aspect of the invention, an optical mirror module has a substrate with a top surface and a bottom surface, and a die. The top surface of the substrate has a top edge portion, while the bottom surface has a bottom edge portion. The die has at least one mirror and circuitry to control the at least one mirror. The optical mirror module further includes a plurality of interface ports adapted to electrically couple the circuitry with a device external to the optical mirror module. The plurality of interface ports are located on one of the top edge portion and the bottom edge portion.
In illustrative embodiments, the module forms a module plane that is substantially parallel to the die. The top and bottom edge portions are spaced from the die on the module plane. The bottom surface of the substrate has a total bottom surface area, and the bottom edge portion may define a boundary for a sub-surface area of the bottom surface. In some embodiments, the subsurface area is more than half the total bottom surface area. In yet other embodiments, the substrate between the bottom edge portion and the top edge portion defines an edge volume containing the at least one interface port.